Proteases or proteinases have a wide application in different industrial processes including cheese production, meat tenderization, production of protein hydrolysates, silver recovery and silk; in many other fields including biotechnological, baking, textiles, pharmaceutical and leather industries and also, as an additive to detergents and in bioremediation procedures. These enzymes are present in plants, animals and microorganisms (protozoa, bacteria, fungus and some types of algae and viruses). Considering the wide applications of these enzymes, it is necessary to know their functions, origin (plants, animals, bacteria and fungus), classification and characteristics, action mechanisms, their specific target substrates and products obtained in the reactions that these enzymes catalyze, as well as their optimal temperature and pH of activity and stability. The book provides an overview of the latest knowledge about the functions and action mechanisms of protease enzymes and their applications in different industrial fields. It addresses four important aspects: the main characteristics of proteases of different origins, the design of emerging technologies for production of novel proteases with enhanced specificity, stability and catalytic activity for a wide industrial application, utilization of proteases to produce functional foods and the use of protease inhibitors to control or block the activity of these enzymes for preventing diseases in humans and animals. It was felt necessary to include a chapter based on the use of bioinformatics resources (databases, tools, visualization and data analysis) to provide a better understanding of proteases and their functions at the molecular level. Although production and application of bacterial and fungal proteases have long been reported, little is known about the proteases produced by insects (mainly those economic and medically important species), organisms inhabiting marine environments and protozoa, their action mechanisms, properties and physiology. This knowledge is important for designing new strategies for herbivory insect control to avoid the transmission or development of pathogens in their corresponding entity hosts (in case of insect digestive proteases), or designing specific antiparasitic drugs to block the action of proteases and avoid colonization and imminent parasitism (in case of protozoa proteases). In addition, the knowledge about the integrity and function of marine proteases under extreme reaction conditions could facilitate their application in a wider processing conditions than the terrestrial proteases.